To many outsiders, cryptography is
a fascinating subject and detailed material is not easily obtainable even
after de-classification. At the turn of the twentieth century, messages
containing confidential information were encrypted using code books and
continued this way up to end of World War 1. In the 1920's, mechanical,
rotor-based machines were developed in Europe and the United States for
the purposes of encrypting commercial business traffic. By the late 30's,
the German military had adapted a three rotor encryption machine that we
now know as the Enigma. Rotor based machines continued to be refined until
replaced by vacuum tube technology and finally, by the computer based technology
of today. One of the most critical applications for secure communications
was the military naval environment. In Canada, around 1962, the KWR-37
was introduced into the Royal Canadian Navy As the radio restoration volunteer
for the ship, it was a strong curiosity towards crypto gear which provided
the inspiration and initiative for the research and story which follows.
The KWR-37 was a very advanced machine when first designed in the 1950's,
but its service life was curtailed when security was compromised in the
mid-1980's.

This KWR-37 example is held by the Communications and Electronics
Museum in Kingston. (Photo by Jerry Proc)

All crypto gear fitted on Canadian
ships in the 1950's and onwards was owned by the National Security Agency
of the United States and was loaned to North Atlantic Treaty Organization
member countries including Canada. This still holds true today and crypto
gear used by all US government agencies is subject to the same strict regulations.
Also included back then, was keying material, key lists, certain rotors,
and key cards. This material came in a variety of editions depending upon
the application. Examples of these crypto packages would be named CANUSEYESONLY
(Canadian only), CANUKUS (Canada, UK, and USA), AUSCANUKUS (Australia,
Canada, UK and US), NATO, ALLIED, and so on. Any edition with the designation
of CANEYESONLY, would have been generated in Canada by the Communication
Security Establishment. In 1962, aboard HMCS HAIDA, a pair of KWR-37's
were fitted on steel racks, and a canvas cover blocked them from view as
the crypto receivers were considered very top secret. The crude canvas
cover, installed by the dockyard workers 35 years ago, can still be seen
today.

GENERAL DESCRIPTION

During World War 2, most 'low level' traffic
from surface ships at sea was manually coded and decoded using code books.
In the post war period, the amount of 'broadcast' traffic continued to
increase to the point where it required some level of automation as manual
decoding could not keep up with the volume of traffic. Automation made
its appearance in the form of a teleprinter based receiving system. The
sole purpose of the KWR-37 was to automatically decipher the encoded fleet
broadcasts which was sent to military ships at sea and other applications
where it was required to decode a steady stream of classified traffic.
On the input side, the '37 was connected to the 60 milliamp current loop
output of a frequency shift converter. The output side of the '37 was connected
to a Teletype page printer.

The shore station started each day's broadcast
at 0000 Zulu and transmitted without interruption for 23 hours and 55 minutes
each day. On shore, the encryption device such as a KWT-37 was synchronized
with a time signal station (CHU or WWV) and the originating station sent
an automatic 'start' signal followed by a continuous stream of encrypted,
non-repeating traffic throughout the day. The decoding 'key' which was
similar to an IBM style punch card had a pattern of randomly punched holes,
and had to be changed daily, prior to the start of the next day's broadcast.
Encryption keys were changed by unlocking a front door on the KWR-37, removing
the existing card, and installing the card that was designated for the
next day. These cards were inserted behind a small door in the front of
the KWR-37 using built-in, alignment pins. The door closed against a block
of small, spring-loaded steel pins. Where a pin touched the paper card,
no signal passed; where a pin poked through a hole in the card and touched
a silver-plated metallic track, a circuit was made. Each card held enough
keys to cover 14 years of usage before the key repeated itself. Used cards
were destroyed on a periodic basis. In addition to the operational key
cards, there were also cards used strictly for testing. Each card in the
test deck, checked a different KWR-37 function. Two of the cards, produced
a distinctive pattern of beeps to indicate proper operation and the technician
had to listen attentively. With care, the test cards could last for years.

KOI-7 card reader with door open. The highly
reflective surfaces of the "return" conductor strips are very evident in
this view.

Closeup of front panel controls and indicators.

Meter dial detail: On the lower scale, note the 1.25 volt nominal
filament voltage marking and the 1 volt low and 1.5 volt high margin levels.
The 30 volt and 60 volt operating voltages on the other two scales have
been aligned with the filament voltage nominal reading.

Detail of receiver start time dial

Rear view and cooling fan.

Connections at rear of machine.

All photos in this table by Jerry Proc

John Dill of Kingsville Texas, was
a crypto mechanic in the USN in the 1960's and 70's, and kindly documented
his experiences with the KWR-37. "The holes in the punched cards directed
the key stream to a series of bistable multivibrators (flip-flops) which
were wired on thirteen printed circuit boards located on the left side
of the machine when one opened the equipment drawer. All the flip-flops
plugged into a motherboard which was positioned horizontally. The active
devices in these circuits were sub-miniature, type 6088 sharp cutoff pentodes
with wire leads and they were made by Raytheon or General Electric. These
tubes were .38 inch in diameter and 1.5 inches long and anchored by metal
clips on each circuit board. The 6088 pentode was also known as type CK522AX.
Depending on circuit design, the 6088 could be driven to produce as much
as 10.5 mw of power at the high end or as little as 1.2 mw at the low end!
One multivibrator stage consisted of two 6088 pentodes for the flip-flop
and one 6418 sub-miniature pentode amplifier, a vacuum tube originally
designed for late generation tube computers. All stages had to be perfectly
balanced, hence the use of resistors with 1% tolerance. Typically, the
pentodes ran at 67.5 volts B+ and the triodes at 100 volts. There were
four flip-flops per board and the entire unit contained approximately 500
tubes!

Mechanically, the '37 was around 22 inches
wide, 24 inches deep and 10 inches high with a case finished in navy cabinet
grey. It could either be rack mounted or positioned on a equipment shelf.
With a weight approaching 100 pounds, it was definitely a two man lift
when being installed. At the rear of the unit there was only three sets
of connections: current loop in, current loop out and power.

OPERATION

Transmissions began at 0000Z and continued
without pause or repetition for 23 hours, 55 minutes each day. Whether
any messages were being sent or not, the 'customers' KWR-37's were on-line,
in sync and receiving the transmitted key stream. In the event of a power
loss or if the unit went out of sync, the operator would have to initiate
a restart. When the sending station stopped transmitting, all receiving
units worldwide would be prepared to receive transmissions for the next
day. If radio conditions were normal, the transmitting station's Auto Start
signal would automatically start the machine. If Auto Start was missed
due to atmospherics, the operator had to late start the unit. This procedure
is discussed further in the text.

On the front panel of the unit, there was a
control composed of two concentric dials; the outer for hours and the inner
one for minutes. Above that, were three miniature switches marked Start,
Reset and Sync. Two small, orange lamps tagged Mark and Space flashed alternately
in time with the incoming signal. Re-synchronization of the KWR-37 required
that the machine be reset, then run it forward in time at high speed to
catch up to, then slightly pass, the transmitting station's key stream.
The operator would set the Hours/Minutes dials to the difference between
0000Z and the current Zulu time. The Hours dial was marked in 1 hour increments
up to 23. Similarly, the Minutes dial was marked in 5 minute increments
up to 55. The Reset switch would then be pressed. This would reset the
flip-flops in the Key Generator and the Internal Clock and ensure that
all these circuits started up from a desired, known, pre-set value. Internally,
the reset signal was routed to the flip-flop stages through the Key Card,
thus changing the initial 'set' state of the Key Generator. Pressing the
Start switch would enable and start the clock which began to drive the
flip-flop stages thus producing the key stream. Activating the Sync switch
would give approximately 15 seconds worth of high clock speed, akin to
a fast forward function.

If for example, the KWR-37 had dropped off-line
at 14 hours into the broadcast day due to loss of ships mains power, and
restoral took 15 minutes, the operator would set 14 hours, 15 minutes on
the dials and hit the Start button. The machine would run in high speed
for several minutes until the clock had advanced the key stream 14 hours
and 15 minutes, at which time it would drop back down to normal speed and
start searching for sync. This process forced the KWR-37 in constantly
comparing it's own internal timing to that which was being sent on the
broadcast. If a clock comparison was unsuccessful, the clock would delete
a pulse, effectively dropping it back in time by a small amount. Each time
this pulse deletion occurred, an audible beep was sounded through a panel
mounted speaker. As the beep rate slowed, it told the operator that synchronization
was approaching. After several seconds of silence the Sync light would
illuminate and the teleprinter (ie Teletype machine) attached to the '37
would start printing. The search for synchronization occasionally required
the flipping the "polarity" switch on the front panel.

If the search for synchronization ran over
several minutes duration, the '37 would alarm again with a steady, irritating,
much-hated tone from the speaker along with the dreaded red Alarm light.
Standard procedure called for resetting the machine and trying again. Since
no two KWR-37's were exactly alike, the presence of the alarm did not mean
that the machine stopped searching for sync. The alarm simply meant that
the allotted amount of time had elapsed, during which, synchronization
should have been attained. In many cases, the '37 achieved sync with the
alarm sounding and the SYNC light on. At this moment, the operator would
silence the speaker and everything would run normally. This was the official
procedure for achieving synchronization.

In practice, however, it was an entirely different
world. An operator would generally attempt the formal procedure. If this
did not achieve results, a whole series of 'homebrew' remedies could be
applied. Among these miracle cures for lack of sync were:

a) Pounding the front panel briskly just prior
to pressing the START switch.

b) Opening the equipment drawer and hitting
the tops of the circuit boards with some hard object such as a mallet or
cleaning brush.

c) Opening the front door; removing the key
card and cleaning the conductive tracks in the rear of the front door with
a rubber eraser. This practice removed the plated silver on the tracks
and was frowned upon.

d) Cleaning the conductive tracks with Teletype
paper or paper money. Since Teletype paper contained trace amounts of oil
to assist with lubrication, this practice was highly discouraged.

e) Rapid and vigorous spinning of the time-delay
dials, followed by many shots on the RESET button.

f) Uttering foul, abusive language at the machine
in order to let it know who was in charge!

John Clingman, an Electronics Technician
in US Navy from 1969-1973, adds this unofficial technique to tame the machine
when it was misbehaving. " I was not trained on crypto, but I talked
with the crypto ETs and helped them with some peripheral maintenance.
During that time, only ETs or RMs who were obligated for at least 6 years,
were trained in the (relatively long) crypto equipment classes.

The rubber-hammer love taps to shake out the
bugs in the KWR-37 is an interesting method of troubleshooting and repair.
This was probably hard on the tubes, but vibrations form the firing of
the ship's guns were pretty rough.

Our KWR-37 tech let me in on a technique that
was sometimes used, and definitely not officially recommended. When
many resynchs had been attempted (and failed), and the C.O. was applying
pressure to get his Fleet Broadcast, sometimes the tech would risk a little
increase in the filament voltage (above nominal.) This could result
in getting the unit back in synch. Of course it weakened the tubes
even faster. After a day or two, the slightly elevated filament voltage
no longer did the trick. Another tweak and maybe it would work for
another watch. Eventually, the weak tubes were beyond help and the
formerly good tubes were also ruined or degraded. With large numbers
of flaky tubes, it was nearly impossible to troubleshoot the unit.
A full set of known good boards was required for a very time-consuming
repair, swapping one sick board at a time into an operational receiver.
A ship did not have that many spare cards, and would not have enough tubes
to replace all the duds. A trip to the crypto shop on a tender or
a shore base was needed. The Captain could be pretty cranky about
a delayed deployment when a receiver was away at the shop."

MAINTENANCE

The KWR-37 originally designed in the 1950's
was very tired and well past it's design life in 1968. It did not improve
with age. Many technicians only had a modicum of training in the art of
soldering. For the '37 family, this was a disaster as the most frequently
performed corrective maintenance involved the replacement of wire lead
vacuum tubes. One can only imagine the damage that was done to the printed
circuit boards after 20 years of mediocre maintenance. To ensure the highest
reliability, crypto mechanics tried to turn out a machine capable of operating
normally with only 1 volt of filament voltage to all the 6088 pentodes.
The standard setting was 1.25 volts and was indicated by a front panel
meter. Each pentode had a filament draw of 20 ma. If the unit ran properly
at a reduced filament voltage, that meant that the tubes had strong emission
and the unit would run reliably. As emission decreased, the operator could
increment the filament voltage to restore normal operation. When the machine
became unreliable at a setting of 1.25 volts, it was turned back to the
maintenance depot. Checking for operation at a reduced filament voltage
became known as 'margining'. The 6418 pentodes which used indirectly heated
6.3 volt filaments were not margined.

Later and unofficially, an extender board was
developed which allowed individual circuit boards to be margined. Once
each board ran reliably at 1 volt filament voltage, the filament supply
to the entire machine was reduced. If it worked, it was considered ready
for use. Testing each board individually improved the quality of the troubleshooting
process. The majority of maintenance problems in the '37 originated in
three areas of the machine: the 'S' circuit cards, (the ones containing
the key stream flip-flops); the 'T' cards which combined the 'S' card outputs
and the 'U' or alarm cards. Next, were the cards which allowed the '37
to run at high speed. The modified card extender was invaluable in finding
these circuit faults and eventually won official approval. A maintenance
bulletin was circulated among all KWR-37 holders documenting the modified
extender, the construction details and stock numbers of the parts required".

John goes on to comment about his worst KWR-37
repair job. "A navy technician had the '37 drawer open for maintenance.
Innocently, a brand new Ensign, who was the ships Communications Officer
noticed the activity and came over for a look. He must have been having
a hard time at sea because of the large bottle of Maalox (stomach antacid)
in his shirt pocket. As the Ensign leaned over to peek at the '37, the
bottle fell out and broke on the top edge of the equipment drawer. Needless
to say, the Maalox spilled throughout the machine and a large blue flash
ensued as the power supply shorted out. Flames and smoke began issuing
from the drawer. The tech had been sitting on the deck in front of the
'37 cross-legged with his legs underneath the extended drawer. His burning
trousers were quickly extinguished by the remainder of the Maalox running
out of the equipment. In his haste to escape, the tech placed his full
weight on the card rack and broke the motherboard in several places. The
'37 was eventually repaired but the cost to repair, likely exceeded the
value of the machine".

CONCLUSION

During it's service life, the security of the
KWR-37 system was essentially compromised from 1968 to 1985. When the USS
Pueblo was captured in 1968, the north Koreans acquired fully working KWR-37's
along with active key cards. Naturally, there was a mad scramble to quickly
change all of the cards held by KWR-37 'customers' all over the world.
In the mid 1980's, it was discovered that the infamous 'Walker spy ring'
was selling active key lists (ie the actual IBM style punched cards) to
the Communists. It must be assumed that this activity had trasnspired
as early as 1968. Once again, the key lists had to be quickly changed.
It's important to note that simply possessing a machine was insufficient
to copy the traffic in the short term. Any adversary had to be in possession
of the active key lists in order to immediately decode any traffic. By
the early 1990's, any remaining KWR-37 crypto receivers were taken out
of service and destroyed. This sounds like a sad ending, but such is life
in the world of cryptography.

As a result of the capture of the USS Pueblo in 1968 by the North
Koreans, the following cryptographic systems were compromised: KL-47, KW-7,
and KG-14 along with the KWR-37. An NSA report dated July 1969, details
the cryptographic losses. A copy
of this report can be found here.

I extend my sincere thanks to John Dill of
Kingsville Texas for providing much of the source material which made this
article possible. Additional information was also contributed by Gregory
McLean of Abbotsford, British Columbia and Cdr. Bob Willson, RCN (Ret'd)
of Toronto, Ontario.

In this view of the chassis, all the circuits
cards and power supply tubes are missing as part of the "sanitization"
process before crypto equipment can be released into civilian hands.

This unclassified VV card for the KWR-37 illustrates circuit design
using sub-miniature tubes.

On this card, there are three sub-miniature tubes, namely, RAYTHEON
CE93258 (JAN6088) pentodes. Also, there are six sub-miniature tubes RAYTHEON
CE93257 (JAN6418) pentodes. The following semiconductors are also in evidence:
2x 1N1518, 1x 2N43 and 2x 2N534 (Photo by Klaus Kopacz DC8HL)

This auxiliary card plugged into a dummy slot in the KWR-37. Besides
holding a cache of spare fuses, it also carried a "tuning wand" (blue item),
The clamp held a small standard screwdriver which is missing. (Photo
by John Dill)

KWR-37 PARTS SECTION

This is the type of pin used in a number of card readers including
the KG-13, KG-14, KWR-37 and KW-26 machines to name a few. The protrusion
at the left is spring loaded. The connecting wire is soldered to the right
side. Pin sample provided by Jerry Myers. (Image by Jerry Proc)

This is one of the four special nuts used to secure the cardreader
contact board. Nut sample provided by Jerry Myers. (Photo by Jerry Proc)

During the era of the electo-mechanical
crypto machine, Greg Moore would like to nominate one essential tool
which would make most machines behave, if for just a while. That tool was
the good old fashioned rubber mallet. Virtually any malfunction (real,
imagined, or one of the evil idiosyncrasies which lurk in the heart
of any good crypto machine) could usually be cured by a reasonable amount
of whacks, applied over the card reader, the plugboard, or to any exposed
part of the unit as most problems were caused by bad connections,
an intermittent short in a tube, which could be "shocked back" to life.
Please note, this was NOT in any way shape or form, OFFICIAL maintenance
procedure, but after the 10th or so crash at 0300, one developed a hearty
sense of animosity toward the darn alarm sounding. With missed traffic,
one would do just about anything to get the equipment operating normally.
The rubber mallet did not leave marks as did the otherwise useful Zippo
lighter which could be extremely embarrassing during inspections by the
Commo Officer.

Greg Moore, former RM1, USN now WA3IVX

**********

THE WALKER SPIES

On 28 May 1985, John Anthony Walker and his son, Michael
Lance Walker were indicted by a Federal grand jury in Baltimore, Maryland
on six counts of espionage. John A. Walker, a retired Navy warrant officer
who had held a TOP SECRET crypto clearance, was charged with having sold
classified material to Soviet agents for the past 18 years. During his
military career, Walker made some investments in which he lost money. To
make up for his losses, in late 1968 at the age of 30, Walker went to the
Soviet Embassy in Washington, D.C., and offered his services for purposes
of espionage. He compromised key cards used for enciphering messages and
also provided information on the encryption devices themselves. At least
a million classified messages of the military services and U.S. intelligence
agencies were compromised by Walker. A Soviet defector said the KGB considered
this the most important operation in its history. Michael L. Walker, a
petty officer assigned to the USS Nimitz, was accused of providing classified
Navy documents to his father for sale to the Soviets. Fifteen pounds of
classified material were in his possession at the time of his arrest on
the Nimitz. On 28 October 1987, both John and Michael Walker pleaded guilty
to espionage under a plea agreement. On 6 November 1986, John Walker was
sentenced to two life terms plus 10 years to be served concurrently. Michael
was sentenced to 25 years. John Walker's arrest was the result of an FBI
tip from his former wife.